Actually there are more than six tools to perform neutral position setting tasks of trimmable horizontal stabilizer elevators of an entire fleet. These tools have different purposes, sizes, and accuracies.
FIG. 1 shows a rigging tool actually used for Wide Body (WB), Single Aisle (SA) and Long Range (LR) aircrafts. This mechanical type tool is formed by an elongated guide (16) to be positioned on the THS extrados skin, and a gauge (17) intended to be placed under one extreme of the guide (16) to measure the deviation between their extremes. This mechanic gauge (17) provides measurements with deviations lower than 0.05°.
To provide a measure, the guide (16) is extended from the THS extrados skin up to the elevator. For that, the size of this type of guides goes from 2 to 3 meters long, which complicates its handling.
Further, it is necessary to have guides of various sizes to cover different types of aircrafts.
FIG. 2 shows another rigging tool actually used for Long Range (LR) aircrafts. This optical type tool is formed by a theodolite (14), a target sight platform (15) and a target plate (22). The showed tool is intended to be positioned on intrados skin, such that the elevator is set in a neutral position when the three components are in line.
This tool is expensive, delicate and very difficult to assemble. Also, although a theoretical accuracy of 0.001° can be reached, the real accuracy usually reached is close to 0.5°, due to its extreme complex design, and the difficult to reach drawing tolerances when the tool is being assembled by the manufacturer.
It would therefore be desirable to provide technical approach(es) that offer a common solution for setting a neutral position on any control surface of an aircraft, while providing good accuracy, and simplifying its use and manufacture.